Size Effect of Nanosheet on BN Fibers Derived from BNNS/Polyborazine Hybrid Precursor

doi:10.15541/jim20250275

Abstract

Abstract:

BN ceramic fibers exhibit significant potential for applications in high-temperature wave-transparent and semiconductor fields, due to their excellent resistance to high temperatures and thermal conductivity, as well as their outstanding wave-transparent performance. However, the low crystallinity observed in BN ceramic fibers inhibits complete realization of their potential superior properties associated with the h-BN crystal structure. In this work, based on the mechanism that inorganic nanofillers could act as heterogeneous nucleating agents to accelerate matrix crystallization, three lateral sizes (0.5, 2 and 4 μm) of amino-functionalized BN nanosheets (BNNSs) were prepared utilizing a one-step ball milling method. BNNSs were chemically bonded to molecular chain of polyborazine to synthesize hybrid BNNS/polyborazine precursors, which were finally derived into high-performance BN ceramic fibers with high crystallinity. This investigation thoroughly explored the scale effects of BNNS on the molecular structure of hybrid precursor, as well as their physicochemical properties and melt spinning performance. Relationship among the BNNSs’ size, microstructure and mechanical properties was elucidated. Increasing BNNSs size could enhance the ceramic yield of precursor (up to 64.1%), but destroy the viscosity-time stability. Moreover, it was demonstrated that BNNS scale could evidently regulate crystal structure of BN ceramic fibers. Relationship among the BNNSs’ lateral sizes, crystal structure and mechanical performance was determined to be non-linear. BN ceramic fibers containing 2 μm BNNS displayed the highest crystallinity (94%), grain size (12.5 nm) and density (2.00 g/cm³). However, surface defects associated with 2 μm BNNS resulted in a non-optimal average tensile strength (0.90 GPa). BN ceramic fibers doped with 0.5 μm BNNS exhibited the best average tensile strength (0.94 GPa), attributed to the favorable combination of high crystallinity and smooth surface. This work could provide crucial references for fine regulation of microstructure and preparation of high-performance BN ceramic fibers.

Key words: BN ceramic fiber, crystal structure, mechanical property, BN nanosheet, BNNS size effect

CLC Number:

TQ343

ZHANG Yunbo, WANG Bing, LI Wei, SONG Quzhi, DU Yi’ang, WANG Yingde. Size Effect of Nanosheet on BN Fibers Derived from BNNS/Polyborazine Hybrid Precursor[J]. Journal of Inorganic Materials, 2026, 41(3): 359-369.

Figures/Tables 12

Fig. 1 Diagram of preparing hybrid polyborazine precursor P-BNNS

Fig. 2 Morphologies and crystal structures of BNNSs with different lateral sizes (a) SEM image of 4BNNS; (b, c) HRTEM images of (b) 2BNNS and (c) 0.5BNNS; (d-f) SAED patterns of 4BNNS, 2BNNS and 0.5BNNS

Fig. 3 Molecular structures and ceramic yields of P-BNNS grafted by BNNSs with different lateral sizes (a) FT-IR spectra; (b) 1H-NMR spectra; (c) Ceramic yields

Fig. 4 Rheological properties of PPMAB and hybrid precursors grafted by BNNSs with different lateral sizes (a) Fitting curves of apparent viscosity (ηa) and shear rate (γω) at 140 ℃; (b) Apparent viscosity-time curves at 130 ℃; (c) Apparent viscosity-temperature curves; (d) Andrade equation fitting curves

Fig. 5 Average diameters of green fibers spun by P-4BNNS, P-2BNNS and P-0.5BNNS at different spinning temperatures and 0.3 GPa Colorful figure is available on website

Fig. 6 Morphologies and corresponding diameter distributions of green fibers spun by three hybrid precursors (a-c) SEM images; (d-f) Diameter distributions

Fig. 7 Surface and cross-section morphologies of BN ceramic fibers derived from different hybrid precursors under the same conditions and schematic diagrams of internal grain arrangement induced by BNNSs with different lateral sizes (a-f) BN ceramic fibers derived from (a, d) P-0.5BNNS, (b, e) P-2BNNS and (c, f) P-4BNNS; (g-i) Schematics of the relationship between BNNS size and crystal structure of BN ceramic fibers

Fig. 8 Crystal structures and mechanical properties of BN ceramic fibers grafted by BNNSs with different lateral sizes (a) XRD patterns; (b) Radar chart of crystallinity, grain size, mechanical strength and density. Colorful figures are available on website

Fig. S1 Lateral size distributions of BNNSs after ball milling for different time (a) 12 h; (b) 24 h; (c) 48 h

Table S1 Crystal structures and mechanical properties of BN ceramic fibers grafted by BNNS with different lateral sizes

Sample	Crystallinity/%	Grain size/nm	I₍₀₀₂₎/I₍₁₀₀₎	Density/(g·cm^-3)	Tensile strength/GPa	Young’s modulus/GPa
BNF-0.5BNNS	90	7.8	5.86	1.96	0.94	102.5
BNF-2BNNS	94	12.5	8.97	2.00	0.90	126.0
BNF-4BNNS	91	11.4	7.67	1.84	0.37	88.7

Fig. S2 Mechanical properties of BN fibers reported in literature and this work[6,25-29]

Table S2 Two-parameter Weibull equation of tensile strength for three BN ceramic fibers

Sample	Shape parameter (β)	Scale parameter (η)/GPa
BNF-0.5BNNS	4.92	1.05
BNF-2BNNS	4.69	0.99
BNF-4BNNS	5.50	0.42

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